package com.app.utils;

import java.security.MessageDigest;
import java.util.Random;

public class MD5 {


	private final static String[] hexDigits = {"0", "1", "2", "3", "4", "5", "6", "7",
			"8", "9", "a", "b", "c", "d", "e", "f"};

	/**
	 * 转换字节数组为16进制字串
	 * @param b 字节数组
	 * @return 16进制字串
	 */
	public static String byteArrayToHexString(byte[] b) {
		StringBuilder resultSb = new StringBuilder();
		for (byte aB : b) {
			resultSb.append(byteToHexString(aB));
		}
		return resultSb.toString();
	}

	/**
	 * 转换byte到16进制
	 * @param b 要转换的byte
	 * @return 16进制格式
	 */
	private static String byteToHexString(byte b) {
		int n = b;
		if (n < 0) {
			n = 256 + n;
		}
		int d1 = n / 16;
		int d2 = n % 16;
		return hexDigits[d1] + hexDigits[d2];
	}

	/**
	 * MD5编码
	 * @param origin 原始字符串
	 * @return 经过MD5加密之后的结果
	 */
	public static String MD5Encode(String origin) {
		String resultString = null;
		try {
			resultString = origin;
			MessageDigest md = MessageDigest.getInstance("MD5");
			resultString = byteArrayToHexString(md.digest(resultString.getBytes("utf-8")));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return resultString;
	}

	//随机生成盐
	public static String generateSalt(){
		String salt = "";
		Random r = new Random();
		StringBuilder sb = new StringBuilder(6);
		sb.append(r.nextInt(999)).append(r.nextInt(999));
		int len = sb.length();
		if (len < 6) {
			for (int i = 0; i < 6 - len; i++) {
				sb.append("0");
			}
		}
		salt = sb.toString();
		return salt;
	}

	public static void main(String[] args) {
		String pwd = "123456";
//		String salt = generateSalt();//生成盐保存到数据库
		System.out.println(MD5.MD5Encode(pwd));
		System.out.println(MD5.MD5Encode(MD5.MD5Encode(pwd)+"375142"));//采用两次md5加密方式

	}

}
